[Zubersoft]

I have the exact same tablet as you (it's my primary tablet for testing), and if I go to Settings->MIDI Settings->Configure MIDI Connections with nothing attached to it, I can switch the dropdown between Default/Google/High-performance. After switching the library, it will stay gray for a second, but then it goes back to white and lets me change it. The first thing we need to do is to identify why this is not working on your tablet. If you have nothing connected, and your tablet is not behaving like this, the next thing to do would be to try installing MobileSheetsFree off the Google Play Store, then repeat the tests in the free version. If that works for some reason, and the paid version does not, then it would probably be worthwhile to backup your library, uninstall the application, reinstall it, restore your library backup and then try to switch the MIDI settings. I know this is tedious, but I don't have an explanation for why your tablet is behaving this way at the moment, so we will have to use trial and error.

Mike